This invention relates in general to environmental pollution and, more particularly, to a method for treating halogen-containing plastic refuse to prevent halogens and halogen compounds from being released for causing environmental pollution. The present method also has application within the field of scrap metal salvage whereby metals normally encased in halogen-containing plastic materials may be recovered.
The disposal of plastic refuse is a continuing problem of ever-increasing proportions confronting our society. The seemingly endless utilization of plastic in industry, as well as in the production of infinite products, causes the concern for disposing of such material after the particular devices have served their intended purposes to be one of almost incomprehensible immensity.
However, in addition to the problems attendant with disposing of the rapidly increasing volume of plastic trash, there exists the more critical matter of disposing of plastics which contain halogen so that the particular treatment will not bring about a release into the environment of either the halogens or compounds thereof. For instance, burning of halogen-containing plastics in the atmosphere would cause the discharge of such halogenic material with imperiling of health, as well as with destructive tendencies to materials incorporated in neighboring constructions. As an example, the release of chlorine either as a gas or as hydrogen chloride would cause development of hydrochloric acid by reason of atmospheric moisture content, and the corrosive nature of such is well known. Experience has also indicated that similar release occurs when halogen-containing plastics are disposed of in land fills.
Although the number of halogen-containing plastics are myriad, those most widely utilized commercially at the present time are polyvinyl chloride, polyvinyl fluoride, and polyvinylidene chloride. But the prospects are that additional compounds of this type will be formulated and will undoubtedly find new uses with enhanced need to effectively treat such material when discarded.
Currently, plastics of the type hereunder consideration have found wide usage for insulation of electrical wires and in view of the aforesaid attendant drawbacks in disposing of such halogen-containing plastics, there have been concomitant difficulties in the recovery of metal covered thereby.
To the present time, techniques for removing polyvinyl chloride coatings from metals have been fundamentally of two types: one wherein the scrap is subjected to mechanical chopping; and the other by burning of the insulation in the atmosphere. With mechanical chopping it has been found that the heat generated by such operation has been sufficient to cause a melting of the polyvinyl chloride with resultant clogging of the equipment, as well as presenting a fire hazard, which, if realized, would cause unrestricted production of hydrochloric acid.
Another drawback of burning in the atmosphere, besides the undesired release of halogenic material to the atmosphere, is the difficulty in controlling the temperature of such burning whereby oxides of the metals to be recovered may be formed as well as a melting of the metal. To the present time salvage of halogen-containing plastic clad metals has been most unsatisfactory.
Therefore, it is an object of the present invention to provide a method for treating halogen-containing plastic refuse to prevent any released halogens or compounds thereof from polluting the atmosphere or bringing about conditions deleterious to neighboring structures.
Another object of the present invention is to provide a method of the type stated which may be most economically performed; which is effective; and which is fully reliable; providing an answer to a problem which has long beset society and which can only serve to remove inhibitions from further research into the use of plastics of such character.
It is another object of the present invention to provide for recovery of metals which are normally coated with halogen-containing plastic materials, as for electrical insulation purposes.
Another object of the present invention is to provide a method of the character stated which is performed with facility and being productive of the original metal without formation of significant quantities of oxides or other undesired compounds; and which is markedly efficient, providing maximum metal yield.
It is a still further object of the present invention to provide a method for salvaging metal from halogen-containing plastic coatings, claddings, encasements and the like, which is of extreme versatility and which requires simplicity of equipment.
It is another object of the present invention to provide a method of the character stated which does not alter significantly the metal salvaged, so that the same is capable of being further processed, if desired, in accordance with current techniques.
It is a fundamental object of the present invention to provide a method which is of anti-pollutional character and simultaneously effective for metal salvage.